Winetech Technical Yearbook 2022

Uninoculated

however, it should be noted that the concentrations of lactic acid above 4 g/L can have an inhibiting effect on MLF. Alcohol • LT2 (sequential) resulted in the wine with the lowest ethanol content (15.6% v/v) amongst the dry wines. • The average decrease in ethanol for the dry-fermented co inoculations was 0.4% v/v, while the average decrease in ethanol for the dry-fermented sequential inoculations was 0.9% v/v. The lower alcohol content reported can be attributed to the partial conversion of sugar to lactic acid and not ethanol in the LT treatments, the extent of which varies between the strains and inoculation regimes. 7, 15 Sensory evaluation • The TA and lactic acid content corresponded well with the sensory panel’s intensity rating of ‘length of acidity’ and ‘perception of acidity’. As a result, the LT samples (especially sequential inoculations) scored higher in these attributes. • The LT wines scored lower in ‘hotness’, ‘bitterness’ and ‘body’ when compared to SC and UN. • The flavour profile of the LT wines was largely shifted towards the ‘red fruit’ spectrum. • The reference to ‘flat/flabby’ was significantly less for the LT wines (especially LT1 and LT2) when compared to SC and UN. CONCLUSION This study demonstrated the capabilities of Lachancea thermotolerans (in co-cultures with Saccharomyces cerevisiae ) to acidify wines, while reducing the ethanol content. This is a valuable tool in situations where musts have high sugar and low acid content. For the production of quality Merlot wines (especially in warmer climates), the use of Lachancea thermotolerans can not only effectively modulate wine acidity and ethanol, but also add flavour balance (‘red fruits’) to the wine, while steering it away from being described as ‘flat/flabby’. It is important to note that certain parameters were more affected by the specific Lachancea thermotolerans strain and other parameters by the inoculation regime. It seems that strain LT2, commercially known as Laffort’s ZYMAFLORE ® OMEGA LT , was particularly well suited for the production of quality Merlot wines. 5, 20 Strains differed significantly in their capabilities and sound scientific results (such as the peer-reviewed article summarised here) should be consulted to ensure the right strain is chosen to achieve the desired effects. REFERENCES https://www.wineland.co.za/steering-away-from-flat-and flabby-merlot/

Ethanol % v/v pH TA (g/L as tartaric acid)

Lactic acid (g/L)

16.2 3.89

4.7

1.7

• Resulted in high-alcohol and low acidity wines (comparable to the control). • Only treatment that completed spontaneous malolactic fermentation (MLF). • Sensory panel rated the wine as the least ‘acidic’ (comparable to the control). • Sensory panel rated the wine high in ‘sweetness’, ‘hotness’ and ‘body’ (probably due to the lower acidity as these attributes did not correspond with the residual sugar levels). • The wines had higher intensity ratings for the sensory attributes ‘VA’ and ‘oxidised’ and had relatively higher acetic acid and ethyl acetate concentrations. • The wines had lower intensity ratings for the sensory attributes ‘red fruit’ and ‘herbaceous’. • Approximately 50% of the sensory panel described the wine as ‘flat/flabby’ (comparable to the control). Lachancea thermotolerans There was variability in the capacity of the five different LT modalities to alter some of the properties. For instance, the behaviour of the low lactate producing strain LT3 was in stark contrast to the LT1 and LT2 strains, which were much more efficient in acidifying the fermenting must. For the purpose of this article, only the results from LT1, LT2, LT4 and LT5 will be discussed. More details can be obtained from the original publication. 5 The table above shows the range of concentrations for the eight different LT treatments (four strains x two inoculation regimes) where the improvement from the SC control and the UN treatment is evident. Acidification Both the strain, as well as the inoculation regime (co-inoculation vs sequential inoculation), had a significant effect on lactic acid concentration, pH and titratable acidity (TA). In general, the delay in SC inoculation (sequential) allowed the LT yeasts to contribute more in terms of lactic acid production and acidification. • The LT treatments resulted in wine acidification (drop in pH and increase in TA) when compared to SC and UN. • Wines with more lactic acid also contained lower alcohol content. • LT1 and LT2 (both sequential) showed remarkable acidification properties delivering the wines with the highest TA and lowest pH values. • The acidification potential of LT4 and LT5 was intermediary (but still a significant improvement from SC and UN). • Deliberate MLF was not conducted in the experimental wines so as to better understand the impact of yeast treatments alone, Ethanol % v/v pH TA (g/L as tartaric acid) Lactic acid (g/L) 15.0 - 16.3 3.36 - 3.71 6.2 - 11.1 1.8 - 8.1

For more information, contact Carien Coetzee at carien@basicwine.co.za.

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WINETECH TECHNICAL YEARBOOK 2022